The present invention concerns a vibration dampener that adapts to different speeds of rotation. The device comprises a hub or "drive collar" and several inertial masses. The drive collar rotates around a central axis and the inertial masses pivot about peripheral axes in the direction of rotation. Each inertial mass is secured to the collar by two bolts. The bolts are parallel to the central axis and are distributed around the circumference of the collar. The bolts roll back and forth along arcs. The arcs are concave toward the central axis in the vicinity of the collar and concave in the opposite direction in the vicinity of the inertial masses.
A vibration dampener of this type is known from the British Patent No. 598 811. In this device the arcs consist of sections of bore walls. The bores are considerably wider than the bolts. In the event of vibration, the bolts roll over the walls, continuously varying the distance between each inertial mass and the central axis during the course of each individual vibration. Since the frequencies inherent in such a vibration dampener are proportional to the speed of rotation, vibrations with frequencies that are also proportional thereto can be eliminated over the whole range of speeds. All cyclically operating machinery, motor vehicle internal combustion engines for example, exhibit such speed proportional frequencies.
The bolts and arcs in this known speed-adaptive vibration dampener are forced toward each other as long as the shaft turns. The inertial masses all revolve around, and are located as far from the central axis as possible as long as the shaft continues to rotate at a constant speed. This state is disrupted, however, when the shaft stops rotating. All of the components then shift, subject to gravity, as far downward toward the earth's center as possible. The inertial masses and bolts distributed around the device will accordingly differ in distance from the central axis.
When speed-adaptive vibration dampeners stop rotating, the transition from motion to rest is unpleasantly apparent when the inertial masses on the other side of the shaft from the earth's center plummet suddenly downward and the bolts collide against whatever section of the metal bore wall confronts them. The result is a loud clang. A similar phenomenon (and noise) accompanies the transition from rest to motion.